David Milne-Home on Ancient Glaciers. 57 
west, where at a distance of about thirty miles, they are only 
1500 feet above the sea. Now, it is important to remark, that 
Mr Neckar describes these deposits as not only containing 
large alpine blocks, but as composed of rounded pebbles and 
gravel, also alpine in their origin. He also adverts to the 
circumstance, that the lowest pleistocene deposits of the district 
are beds of gravel and sand, arranged generally in horizontal 
beds, and which seem to have been deposited in currents of 
water. In these lowest beds, no erratic blocks are ever found. 
It is in the upper set of deposits that they occur, and the 
lowest of which generally consists of finely comminuted clay, 
on which are situated the numerous brick-works before alluded 
to on both sides of the lake. ‘ 
There is another important fact to be kept in view in the 
consideration of this matter, that it is towards the east end of 
the Lake of Geneva, and near or opposite to the mouth of the 
valley of the Rhone, that erratic blocks occur of great size, 
in great numbers, and at apparently the greatest altitudes. 
Mr Neckar describes many on the north-west of Neufchatel 
Lake as occurring at a height of 3575 feet above the sea, and 
at the east end of the Lake of Geneva at a height of 3550 feet, 
whilst on the south side they occur at the height of 3265 feet ; 
all of which altitudes, it will be observed, are greater than 
those given for the altitudes of the blocks to the west of 
Geneva. 
III. Inferences. 
1. After what I saw of the mechanical effects of the Mer de 
Glace on the adjoining rocks, I formed a very decided opinion 
that the evidence is undeniable of the existence of a glacier, 
which in ancient times filled the whole valley of Chamouni, 
and, descending along the present course of the Arve, was 
capable of depositing on the Petit Saléve and intervening 
mountains the alpine blocks which are now strewed over them. 
If this was the case with the valley of the Arve, I cannot 
hesitate to admit that the larger valley of the Rhone must 
have been occupied by a glacier of corresponding size, which, on 
emerging from that valley would pass across to the plains of the 
Jura, and then turn towards the west and lower extremity of 
NEW SERIES.—VOL XIV, NO. I.—JuLy 1861. H 
